Men look for survivors after an earthquake in southwest China's Yunnan Province on Aug. 3. / Hu Chao, AP

by Calum MacLeod, USA TODAY

by Calum MacLeod, USA TODAY

BEIJING â?? A strong earthquake struck a remote, mountainous part of China's southwest Sunday, killing at least 381 people, injuring more than 1,800 and toppling more than 12,000 homes, state-run media reported.

The U.S. Geological Survey said the magnitude-6.1 quake struck at 4:30 p.m. local time. The China Earthquake Networks Center measured the quake as magnitude-6.5 and said the epicenter was in Ludian County, in the city of Zhaotong in southwest Yunnan province - a known earthquake belt.

Most of the deaths - 357 - were in Zhaotong, the state-run Xinhua News Agency reported. Ten others were killed in Quijing City.

It was the strongest quake to hit Yunnan province in 14 years, Chinese state broadcaster CCTV said.

In a typically robust response, Chinese authorities quickly dispatched thousands of soldiers to assist local firefighters and other emergency workers. Premier Li Keqiang also arrived in the region Monday morning to direct relief efforts, said Xinhua.

As search teams scoured the rubble for survivors Monday, two military helicopters and two cargo planes were en route to the quake zone, with relief supplies including tents, reported CCTV, the state broadcaster. Delivering these goods to the worst-affected areas remains highly challenging after landslides and ongoing rainstorms.

"The blocked roads and the continuous downpour have made some disaster areas inaccessible for the relief vehicles," Liu Jianhua, the senior official in Zhaotong as head of the city's Communist Party committee, told the Xinhua news agency. Over 1,500 residents in Huodehong township were evacuated as a quake lake threatened the township, where the earthquake killed 21 and left another 30 missing, said Xinhua.

Home to 23 different ethnic groups, this quake-prone part of northeast Yunnan is also one China's poorest areas.

In Washington, the White House offered its condolences and help.

"The United States stands ready to assist," National Security Council deputy spokeswoman Bernadette Meehan said.

Ma Liya, a resident in the Ludian County seat of Zhaotong, told Xinhua that the streets were like a "battlefield after bombardment." Transportation, electricity and telecommunications were cut off in the county, the news agency said. CCTV showed emergency workers climbing over large boulders that had fallen and blocked roads in the mountainous and poor region.

Aftershocks, landslides, rain and thunderstorms are hampering rescue efforts, the People's Daily newspaper and the website Sina.com reported. Heavy rains are forecast for the next three days.

Since the massive 2008 earthquake in neighboring Sichuan province that left nearly 90,000 people dead or missing, China has invested heavily in a national earthquake monitoring and early-warning system that cannot forecast a quake but may be able to notify people seconds before seismic waves reach their area.

The China News Service, a state-run news agency, said Sunday that local seismology bureaus had issued warnings for Zhaotong 10 seconds ahead of the quake reaching the city and gave a 57-second warning for the provincial capital, Kunming.

In Sichuan's Yibin City, the Yibin News website reported residents had received cell-phone warnings 40 seconds before the quake. The official Yunnan.cn website quoted a seismic expert who was skeptical of the warnings claimed in Chinese media reports.